U.S. Pat. No. 4,063,570 (Mitchell et al. 1977) is an example of a plumbing valve. This plumbing valve has a valve flap which pivots away from a seat to allow flow in one direction, but engages the seat to prevent flow in the opposite direction. U.S. Pat. No. 566,110 (Wrigley 1896) is an early version of a cleaning device used for plumbing installations, which has come to be known as a “plumbing snake”. A plumbing snake would not normally be used on plumbing lines having a plumbing valve, such as disclosed in the Mitchell et al reference. The valve flap pivots away from the seat to allow the plumbing snake to be inserted, but pivots back toward the seat, wedging the plumbing snake against the seat of the plumbing valve and preventing it from being withdrawn.